What is mcpi?
mcpi is a native MCP inspector for macOS — one Rust binary that does two jobs:
- Diagnose the connection. Point it at an endpoint and get a real answer instead of a generic connection error: wrong path, an auth model your client can't complete, a server still speaking a deprecated transport.
- Classify the change. Every server's contract is recorded locally. Reconnect after a release and mcpi shows exactly what moved — each change judged breaking, compatible, or cosmetic.
The judgement is the product. A wall of before/after JSON is what you already get from squinting at two terminal windows; mcpi leads with "1 breaking" and keeps the evidence one click away.
What the app does
All of it, free forever — no account, no trial clock, no licence:
- Connect over stdio and streamable HTTP, including OAuth sign-in
- Browse tools, resources, and prompts
- Call any tool from a form generated from its input schema
- Replay calls from history
- Endpoint check: diagnose a URL before you ever connect
- Every connect compared automatically against the last recorded contract
- The full diff drawer: changes classified and grouped, exportable as Markdown
- Baselines: pin a recorded contract under a name ("v1.2") and diff any two moments
- Collections: saved call sequences, run as one-click smoke tests
Nothing that runs on your machine is paid. What is paid runs on ours — scheduled checking of an endpoint, and telling someone when it moved. See the pricing page for what that covers.
The CLI
mcpi-cli is the free, CI-shaped surface over the same engine: snapshot a contract as JSON, diff two contracts, exit 1 on breaking. It reads the same baseline pins the desktop app writes.
Where your data lives
Servers, snapshots, call history, and collections live in a single SQLite file on your disk (~/Library/Application Support/mcpi). OAuth tokens and API keys go to the macOS Keychain, never into the database. Nothing leaves your machine.